POS0871 ROLE OF INFLAMMATORY BURDEN AND TREATMENT ON JOINT SPACE WIDTH IN PSORIATIC ARTHRITIS-A HIGH-RESOLUTION PERIPHERAL QUANTITATIVE COMPUTED TOMOGRAPHY STUDY
Authors: Y. Jin, I. T. Cheng, H. So, D. Wu, J. F. Griffith, V. W. Hung, L. Qin, C. C. Szeto, A. W. Chan, L. S. Tam
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Psoriatic Arthritis (PsA) is associated with enthesitis and synovitis which lead to bone erosions, cartilage loss, and new bone formation. High-resolution peripheral quantitative computed tomography (HR-pQCT) enables the quantitative 3D assessment of joint space width (JSW) with superior resolution compared to radiography. Whether disease-specific parameters are associated with JSW on HR-pQCT in PsA remains uncertain. <h3>Objectives</h3> To assess HR-pQCT joint space outcomes by comparison with radiographs and investigate the relationship between disease-related variables and JSW on HR-pQCT in PsA patients. <h3>Methods</h3> PsA patients who underwent HR-pQCT examination (XtremeCT I, SCANCO Medical AG, Brüttisellen, Switzerland) of the second to fourth metacarpophalangeal joint (MCPJ 2-4) were recruited in this cross-sectional study. The joint space metrics included joint space volume (JSV), mean, minimum (Min) and maximum (Max) JSW, JSW asymmetry (Asymm) and distribution (SD). Volumetric joint space was quantified using an algorithm developed by consensus from the Study group for eXtreme Computed Tomography in Rheumatoid Arthritis (SPECTRA). The joint space domain on standard radiography was scored using the Sharp/van der Heijde (SvdH) joint space score. A generalized estimating equation (GEE) was used to estimate the ability of HR-pQCT to predict SvdH scores. Linear regression models were used to determine the association between disease-related variables and JSW. <h3>Results</h3> 67 patients [47 (55.2%) males; median age: 57.0 (53.0, 63.0); median disease duration: 21 (16, 28) years] were included in this analysis. Most had mild disease activity [Disease Activity index for PsA (DAPSA): 10.1 ± 6.6]. 56/67 (84%) were on conventional synthetic disease modifying anti-rheumatic drugs (csDMARDs) while 27/67 (40%) were on biologic DMARDs (bDMARDs). 11 MCPJ 2, 9 MCPJ 3 and 7 MCPJ 4 were excluded due to poor image quality. Individual MCP joint space parameters were presented in Table 1. Subluxations were detected more frequently by HR-pQCT than radiographs. SvdH score was negatively associated with a lower mean, Max and Min JSW; and higher JSW SD and Asymm (all p&lt;0.05). Multivariable linear regression analysis showed that males had larger JSV (MCPJ 2-4), mean (MCPJ 4) and Max JSW (MCPJ 3). Longer disease duration (MCPJ 2-3) and higher ESR level (MCPJ 3) were negatively associated with mean and Max JSW, while higher damage joint count was negatively associated with mean and Min JSW (MCPJ 2) (Figure 1). Use of csDMARDs was negatively associated with Min JSW (MCPJ 3); while use of bDMARDs was positively associated with Min JSW (MCPJ 2). <h3>Conclusion</h3> HR-pQCT could be widely used for assessing joint damage prior to evidence of radiographic joint damage in PsA patients. Higher inflammatory burden as reflected by longer disease duration, higher ESR levels, and damage joint count was negatively associated with mean, Max, and Min JSW, while suppression of inflammation using bDMARDs seems to prevent a decline in JSW. <h3>Acknowledgements</h3> We are immensely grateful to patients, physicians, and the study personnel. <h3>Disclosure of Interests</h3> None Declared.